Year: 2026
Type: preprint
Abstract: Ultra-short-period (USP) rocky exoplanets can have dayside temperatures high enough to maintain permanent magma oceans, sitting at the intersection of interior geophysics and atmospheric chemistry. Coupled feedbacks between the molten surface and outgassed atmosphere can sustain or enhance a volatile envelope, while stellar interactions can erode it. Understanding which outcome prevails, and its observable imprint, requires a multi-target approach across planets at different stages of thermal evolution. We present predictions for the five targets of JWST Cycle 4 program 8864: TOI-1807 b, TOI-2260 b, TOI-431 b, TOI-6255 b, and TOI-2431 b. Using the PROTEUS coupled interior-atmosphere framework, we construct a simulation grid and classify outcomes into six categories, defined by the final interior melt state and by whether the planet retains a detectable atmosphere thick enough to redistribute heat to the nightside. For targets retaining a non-negligible volatile envelope, our models predict higher partial pressures for most species when the surface is molten, except for S$_{2}$, whose enhancement in the solid regime suggests it may serve as a tracer of interior melt state. Despite some targets showing outcomes across multiple scenarios, most tend toward a bare-rock end-member, with global melt fraction $\leq$ 20\% and atmospheric retention sensitive to escape efficiency. Our analysis reveals a minimum escape efficiency threshold below which volatile envelopes survive under energy-limited escape, constraining the conditions required for atmosphere survival on irradiated rocky planets. These predictions will guide interpretation of MIRI-LRS phase curve observations and identify which targets and features best discriminate between competing geophysical states.
Source: arXiv (Cornell University)
Authors: Sastre, Mariana, Lichtenberg, Tim, Dang, Lisa, Piette, Anjali, Wang, Haiyang S., López-Morales, Mercedes, Wilson, Thomas, Boukaré, Charles-Édouard, Herath, Mahesh, Cowan, Nicolas, Zaman, Md Abdullah Al, Barber, Madyson G., Brinkman-Traverse, Casey, Connors, Nicholas, Crossfield, Ian, D'Aoust, Lina, Herbort, Oliver, Janssen, Leoni, Kervazo, Mathilde, Lammert, Owen, Miguel, Yamila, Pierrehumbert, Raymond, Vazan, Allona, Wardenier, Joost P., Zieba, Sebastian
Institutions: University of Groningen, University of Waterloo, University of Birmingham, University of Copenhagen, University of Warwick, Trottier Space Institute at McGill, McGill University, University of North Carolina at Chapel Hill, Université de Montréal, University of Kansas, University of Vienna, Leiden University, Leiden Observatory, Open University of Israel, University of Bern, Center for Astrophysics Harvard & Smithsonian
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Space Telescope Science Institute, European Commission, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Rijksuniversiteit Groningen, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, HORIZON EUROPE Framework Programme, Canadian Space Agency
Awards: G15659259, G1807707695, G2191281307, Phasenübergänge und Instabilitäten, G433322167, PRELIFE - Pathways, Reactions, and Environments leading to LIFE: An interdisciplinary approach., G58316358, G6273510985, G6686480456, G8992028881, Understanding exoplanet atmospheres through high-resolutionspectroscopy, Non-variant antigens of trypanosomes as potential target for vaccination
OpenAlex ID: W7213609267